Submarine signal control device



April 29, 1969 w. H. REAMS SUBMARINE SIGNAL CONTROL DEVICE Sheet Filed NOV. 28, 1967 H QZ INVENTOR William H. Reams April 29, 1969 w. H. REAMS 3,440,960

SUBMARINE SIGNAL CONTROL DEVICE Filed Nov. 28, 1967 Sheet 2 of 2 74 SEAWATER BATTERY DELAY SQUIB I74 /5 6 /44 L96 L92 /36 I94 /42 /36 Unite 3,440,960 Patented Apr. 29, 1969 US. Cl. 102-16 15 Claims ABSTRACT OF THE DISCLOSURE A hydrostatic fuze having a housing with a central axial cavity, a plurality of electrical contacts disposed on the inner surface of the housing, an elongate piston slidably positioned in the cavity but partially exposed to hydrostatic pressure, a plurality of electrical contacts disposed on the outer surface of the piston, a diaphragm circumferentially disposed between the housing and the piston to form a fluid-tight seal, a spring urging the piston against the hydrostatic pressure so that the piston position is a function of hydrostatic pressure. An explosive squib is secured to the piston for movement into an explosion chamber upon movement of the piston in response to hydrostatic pressure.

Background of the invention This invention relates generally to a control system for an underwater-launched vehicle and more particularly to an electromechanical hydrostatic fuze for a submarine signal device.

Present day manned marine vessels ordinarily carry signal and/or marker devices for a number of reasons but primarily to expedite aerial searches for the vessels should the vessels he in distress. Such devices are relatively simple for surface ships and a wide variety of signals and markers are available. However, suitable signal devices for submarines are necessarily more complex in nature since launching occurs at a submerged level which is generally too deep to be seen by either aircraft or surface ships. The complexity of submarine signals coupled with the fact that present day submarine design makes it difiicult to compartmentalize or isolate the signal prior to launching, has created serious safety problems in storing and launching such signals. For example, should a premature detonation of the first phase of a submarine signal occur, the toxic lay-products generated by the signal are difficult to contain and would spread throughout a large portion of the ship, adversely affecting the operation and safety thereof. Moreover, there is the additional hazard of shrapnel if the signal payload ejection charge is prematurely detonated. These shortcomings in the safety of the storage and launching of submarine signals are particularly acute for a signal of the type having aerially displayable smoke and illumination devices; and it was found to be necessary to redesign the fuzes for such signals in order to meet the safety requirements for submarines in fleet use. These fuzes have widespread applicability, however, to any underwater-launched vehicle.

Summary of the invention Accordingly, one object of this invention is to provide a submarine signal having safety features which reduce the dangers resulting from inadvertent ignition.

Another object of the invention is the provision of a submarine signal having improved safety and reliability.

Still another object of the present invention is to provide a new and improved hydrostatic fuze for a submarine signal.

A further object of the instant invention is to provide an out-of-line ignition system for a submarine signal.

Briefly, in accordance with one embodiment of this invention, these and other objects are attained by providing, in a submarine signal having a pyrotechnic payload, the combination of a spring-urged piston which is responsive to hydrostatic pressure, an explosive device secured to one end of the piston, and a housing providing an explosion chamber whereby movement of the piston will result in the explosive device being disposed within the explosion chamber. Preferably the explosive device is electrically actuated by a circuit including a sea water battery which is activated upon launching the signal; appropriate electrical switching is performed in response to the hydrostatic pressure by a plurality of contact brushes mounted on the housing and corresponding contact rings mounted on the piston.

Brief description of the drawings A more complete appreciation of the invention and many of the attendant advantages thereof will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is a diagrammatic side view of an underwaterlaunched submarine signal in section showing the fuze of the present invention;

FIG. 2 is an enlarged side view of the fuze of the present invention in section",

FIG. 3 is a schematic diagram of the circuit of the preferred embodiment; and

FIG. 4 is an enlarged detailed view in section of a portion of the fuze shown in FIG. 2.

Description of the preferred embodiment Referring now to the drawings wherein like reference characters designate identical or corresponding parts throughout the several views and more particularly to FIG. 1 wherein reference numeral 10 indicates generally a submarine-launched vehicle for providing a surface display, such as a smoke and illumination signal package 11 carrying a pyrotechnic payload and having a fuze 12 therein. The smoke and illumination signal package 11 illustrated herein represents but one of many environments in which fuze 12 of the present invention may be utilized. Accordingly, the details of the signal to be discussed herein should not be considered as limiting the applicability of the fuze but rather as contributing to a better understanding of the operation of the fuze and the apparent advantages therein.

Signal 10 has a cylindrically shaped outer casing 14 and a cylindrically shaped inner casing 16 slidably mounted with respect to each other in a telescoping relationship. Although after launching, water enters a port 18 and occupies an annular chamber 20 formed between the inner and outer casings, the interior of the signal is sealed by an O-ring 22 positioned in a groove 24 in a piston 26 and urged against the inner surface of outer casing 14. In its contracted position, as illustrated in FIG. 1, signal 10 is slightly negatively buoyant; but expanded to its full length, by means to be described hereinafter, the signal is positively buoyant for reasons which will become apparent. Located at the forward end of the signal is a nose assembly 28; positioned intermediately within the inner casing 16 is the pyrotechnic display package and ejection assembly 11; and a switching assembly 32 is in the tail portion of the signal 10. As will be readily understood when considered in connection with the detailed description of the switching assembly, the nose assembly 28 provides the telescoping expansion of the signal and ultimately causes separation of the inner casing from the outer casing, and the pyrotechnic display package and ejection assembly 11 creates an aerial display of smoke and illumination.

As more clearly shown in FIG. 2, switching assembly 32 is secured to a tail casing 34 by any conventional means such as a plurality of bolts 36; and the tail casing is secured to the inner casing by means of a threaded transition casing 38. The fuze 12 has a guide block 40 external of the tail casing which is secured to a stabilizing fin 42 by a retaining pin 44. The guide block fitsinto a longitudinal slot (not shown) in an ejector tube (also not shown) extending the full length thereof to prevent signal 10 from rotating as it leaves the ejector tube. Within the longitudinal guide block slot in the ejector tube, there is a smaller interrupted longitudinal slot (also not shown) which begins at the rear of the ejector tube,-extends forward, but terminates at approximately the mid-point of the tube. This smaller interrupted slot slidably accommodates the upper tip of a break-off arm 46 which extends beyond guide block 40.

The break-01f arm is secured by a nut 48 or other conventional fastener to an elongate piston member 50 at a reduced end portion 52 thereof extending through an opening 54 formed in tail casing 34; the break-off arm is urged against the tail casing between which members there is compressed a conventional seal, such as O-ring 56, which eifectuates a fluid tight seal. Initially and prior to launch ing, piston member 50, which may be made from a magnesium alloy, is axially restrained in its rearmost or safe position by nut 48 and another conventional stop means, such as steel snap or lock ring 58 seated in a groove 60 in a central, enlarged portion 62 of piston member 50.

The piston member 50 is provided with an axial bore 64 at reduced end portion 52 which is fluidly sealed by a plug 66. The piston member further has a weakened portion provided by an annular V groove 68 formed on its outer surface, the V groove being longitudinally aligned with break-off arm 46. A plurality of flooding ports 70 are formed in piston member 50 to provide fluid com munication between bore 64 and a battery cavity 72 provided by tail casing 34. Located within battery cavity 72 and mounted on reduced portion 52 of piston member 50 is a conventional seawater battery 74 which is kept dry and inactive in the sealed battery cavity prior to launching of the signal. The entire switching assembly 32 is fixedly secured to tail casing 34 by any conventional means such as the aforementioned bolts 36 extending through a flange 78 of a cylindrical housing member 80 and threaded into an internal flange 82 of tail casing 34. Compressed between flange 78 of housing member 80 and internal flange 82 of tail casing 34 is a ring-shaped diaphragm 84. On the outer circumferential edge of the diaphragm is an enlarged lip 86 which is seated in an annular groove 88 in flange 78 in such a manner as to secure the diaphragm between flange 78 and flange 82 in a fluidly-sealed relationship. On the inner circumferential edge of the diaphragm is a similar enlarged lip 90 which is seated in an annular groove 92 in a flange 94 of enlarged portion 62 of piston member 50. Lip 90 of diaphragm 84 is compressed in the annular groove 92 by a disc 98 which is urged against enlarged portion 62 and flange 94 thereof by a nut 100 threaded onto reduced portion 52 of piston member 50 in such a manner as to secure the diaphragm to the piston member in a fluidlysealed relationship. Hence, by means of diaphragm 84, the battery cavity 72 is fluidly-sealed off from the remainder of the fuze.

Piston member 50 is slidably mounted with respect to housing member 80 in a piston-cylinder relationship by :he engagement of flange 94 on enlarged portion 62 of :he piston member with an enlarged bore 102 in the housng member. Piston member 50 is urged rearward by a iasing means, such as coiled spring 104 encircling the :nlarged portion of the piston member and compressed between flange 94 thereof and an internal flange 106 on the housing member. The housing member also defines an internal flange 108 which serves as a stop for the piston as will be more fully discussed hereinafter.

At the forward extremity of piston member 50, there is attached, by any convenient means, a squib holder 110 having a plurality of squib firing holes 112 and containing an electrically energizable delay squib 114. Although other means for fastening the squib holder to the piston are within the contemplation of the present invention, the squib holder is preferably attached by a plurality of prongs 116 with internal grooves 118 which snap over an external flange 120 on a reduced portion 122 of piston member 50 near the forward end thereof, thereby completely encapsulating the squib. The disclosed fastening technique has been found to be more advantageous than a threaded coupling since the latter may become loose during handling and thereby unthread itself forward into the armed position which will be explained hereinafter. Furthermore, if the disclosed snap-on squib holder is not properly seated and protrudes forward, any fluid generated therein can vent through the openings between the prongs to minimize the amount of gas which might otherwise vent through squib firing holes 112.

As previously mentioned transition casing 38 connects tail casing 34 and inner casing 16 by any convenient sealing and coupling means. Transition casing 38 further has an end plate portion .124 in which there is formed a squib firing cavity .126 and an exit port 128 providing fluid communication between the squib firing cavity and a chemical delay 130. Surrounding the rearward opening of squib firing cavity 126 is a conventional apertured seal 132 which is fixedly secured by a retainer plate 134 which is bolted intoend plate portion 124.

Surrounding reduced portion 122 of piston member 50, there is an electrical insulating material, such as plastic insulating bushings 136, which may be secured to the piston member by any conventional means, such as bonding by a suitable adhesive or such as press-fitting. As between these two techniques, bonding has been found more practical since press-fitting requires very close tolerances and since the insulating bushings tend to split when pressed onto the piston because the bushing material is usually relatively brittle. It is within the contemplation of the present invention that the above mentioned insulating material may take the form of an injection molded unitary member which would eliminate the production of individual bushings and the process of individually stacking them on the piston as herein disclosed. Positioned in axially spaced annular recesses formed in the bushings 136 are a plurality of electrical contact rings 1-38, 140, 142, 144 and 146 which may be brass with silver plating applied to the contact surfaces or which may be solid silver. These contact rings are illustrated in FIG. 2 but not identified by.reference numeral therein; the reference numerals refer to the designation of the contact rings as shown schematically in FIG. 3. Conveniently, the enlarged portion of the piston member, the insulating bushings, and the contact rings form a smooth contiguous cylindrical surface.

The housing of switching assembly 32 is made up of housing member 80 and a plurality of similar shaped cylindrical housing sections 148, 150, 152, v154, 156, 15-8 and between which are positioned a plurality of electrical brushes 162, 164, 166, 168, 172, 174 and 176 shown schematically in FIG. 3. Brush 162 is disposed between housing sections 148 and 150; brush 164, between housing sections .150 and 152; brush :166, between housing sections 152 and 154; brushes :168, 170 and 172, between housing sections 154 and 156; brush 174, between housing sections 156 and 158; and brush 176, between housing sections 158' and 160. The housing sections are made of any suitable electrical insulating material and may be coupled together and to housing member 80 in any suitable manner, such as by bolt 178. The physical U therewith; this interconnection V sented by broken line 182. Seawater battery 74"is con-' connection of lead wires to the brushes between the housing sections may be accomplished by any conventional manner (not shown). Conveniently, the housing sections form a cylindrical opening of a diameter sufiiciently large to accommodate the cylinder formed by the enlarged portion of the piston member, the insulating bushings, and the contact rings. Attached to the outside of the switching assembly 32, by conventional means (not shown) is a switching device, such as a single-action, one-way, explosive switch .180, for use in the electrical circuit to be discussed hereinafter.

Referring now to FIG. 3, there is shown the electrical circuit of the invention illustrated with the piston movement orientation opposite to that of FIGS. 1, 2 and 4. Contact rings 138, 140, 142, 144 and 146 are gang mounted to the piston member so as to be movable in unison is schematically reprenected to contact rings 138 and 140, and delay squib 114 is connected to contact rings 144 and 146. Contact ring 142 merely serves to short out stationary brushes 168, 170 and 172. when the piston is in the initial position, as illustrated, and to unshort these brushes when the piston is in any other position as will be explained later; hence, there are no components physically attached to contact ring 142. Explosive switch 180, having normally closed contacts 184 and normally open contacts 186, is connected at one terminal thereof to blushes 1-62 and 172 and at the other terminal, through normally closed contacts 184, to brush 166 and brush 168. A gas generating squib 188, physically located in the forward end of signal 10, is similarly connected at one terminal thereof to brushes 1'62 and 172 and at the other terminal to brush 166. A detonator .190 is connected at one terminal to brush 170 and, through normally open contacts 186, to brush 164; the other terminal of the detonator is connected to brushes 172 and 162. Brush #176 is connected, through normally open contacts 186, to brush 164; and brush 174 is connected to brush 162.

Referring now to FIG. 4, an enlarged detail view of bushings 136 and contact rings 142 and 144 is illustrated and described here for purposes which will become apparent when considered with the operation of the fuze. In the smooth contiguous cylindrical surface provided by the bushings and contact rings, there is an annular groove 192 having a flat bottom surface 194 which is parallel with the axis of piston member 50. The forwardmost edge 196 of the groove 1'92 terminates at a point in axial alignment with contact ring 144.

It is helpful to consider the operability and safety features of the fuze of the present invention by considering it in combination with the utilization of the signal itself which can be divided into a sequence of three periods:

(1) storage and pre-launch, (2.) launching and ascending, and (3) nearing surface and surface.

Storage and pre-launch The fuze of the present invention and the signal are depicted in FIGS. 1-3 in the storage and prelaunch configuration. In its initial configuration, the inner and outer casings :14 and 16 are telescopically contracted to a shortened overall signal length of, for example, 39.5 inches; and the weight of the signal is carefully controlled so as to be very slightly negatively buoyant in the contracted position.

Piston member 50 is secured relative to the signal by break-off arm 46 and nut 48 at one end and lock ring 58 in groove 60 in enlarged portion 62 of the piston member at the other end. This initial or pre-launch position may also be referred to as the safe" position since, when the piston member is in this rearmost position, the squib firing holes 112 are positioned behind, or out-of-line with, the squib firing cavity 126. In fact, due to the fluid tight seal provided between end plate portion 124 and squib holder 110 by seal 132, any premature activation of delay squib 114 would not initiate chemical delay because the fluids generated thereby are sealed off from squib firing cavity 126, exit port 128, and the chemical delay itself. Experimental results have indicated that although the safety and reliability of the fuze are enhanced by maintaining a fiuid tight seal around the squib firing cavity, the device is operable without a positive sealing means. With the seal 132 omitted from the embodiment herein disclosed, tests indicate that there is very little probability of initiating chemical delay 130 if delay squib 114 is prematurely activated in its safe or out-of-line position; moreover, additional tests indicate that there is still a high reliability in imitating the chemical delay when the delay squib is activated in its armed or firing position, to be described hereinafter, without such a seal. It is apparent that the seal is not essential to the safety or operation of the fuze, particularly if these portions are made to close tolerances; but the use'of the'seal does increase the safety and reliability.

There are a number of electrical safety conditions created in the fuze in the initial position which can be best observed by reference to the circuit in FIG. 3. First, there is an electrical short circuit across gas generating squib 188, which is connected to brushes 166 and 172, since contact ring 142 connects brush 172 to brush 168 which is connected to brush 166 by appropriate lead means. Second, there is an electrical short circuit across detonator 190, which is connected to brushes 170 and 172, by contact ring 142. Third, there is an electrical short circuit across explosive switch 180, which is connected through normally closed contacts 184 to brushes 166 and 172, by contact ring 142, brush 168, and appropriate lead means. Each of these short circuits is sufficient to prevent the gas generating squib 188, detonator 190, and explosive switch from being energized by a prematurely applied electrical voltage. In addition, it should be noted that delay squib 114 is not even in the main circuit in the pre-launch configuration.

Launching and ascending When the signal 10 is launched from the ejector tube (not shown), guide block 40 slides along the uninterrupted slot (also not shown) in the wall of the ejector tube to prevent the signal from rotating as it is ejected. The breakolf arm 46 similarly slides along the smaller interrupted slot (also not shown) with the aforementioned guide block slot until the tip of the break-01f arm strikes the end of the smaller slot and is pushed rearward due to the stopping action of the end of the smaller slot. As the tip of the break-01f arm is pushed rearward, the retaining pin is withdrawn from the guide block thereby permitting the guide block to fall free and clear of the signal as it leaves the muzzle of the ejector tube. It is, however, within the scope of the present invention that the guide block be removably attached by other conventional techniques or that it might be permanently attached.

It should be apparent that when, during the ejection, the break-off arm is forced rearward upon striking the end of the smaller slot, a bending moment is exerted upon reduced portion 52 of piston member 50 thereby causing the end of the piston member to snap off at the weakened V-groove 68 and to fall away. Thus, seawater enters bore 64 of the piston member and fiows through flooding ports 70 into battery cavity 72 and ultimately into seawater battery 74 thereby activating the latter. The removal of the tip of piston member 50 at V groove 68, in addition to providing the aforementioned seawater flow conduit, also frees piston 50 member for longitudinally sliding movement in a forward direction.

After launching of signal 10 and severance of the tip of the piston member, two opposing forces will act on the piston member. The seawater in the battery cavity 72 exerts hydrostatic pressure against diaphragm 84 and disc 98, tending to move piston member 50 forward into the signal. It is further apparent that, since the area upon which the hydrostatic pressure acts is constant, the force urging the piston member forward will be a linear function of the hydrostatic pressure which is, in turn, linearly proportional to the depth. The other force acting on the piston member is that exerted by spring 104 which preferably is finely calibrated and has a substantially constant spring constant through the operational limits herein involved so as to exert a force which is a linear function of its axial length. The results of the interaction of the hydrostatic pressure force and the spring force are that piston member 50 is responsive to environmental hydrostatic pressure and that the longitudinal position of the piston member is proportional to the instantaneous depth of the device. Hence, since the signal is launched at its greatest depth where the hydrostatic pressure is highest, the piston member will slide as far forward as it can go until flange 94 on piston member 58 strikes internal flange 108 on housing member 80 which serves as a stop; the piston member therefore moves from its safe or rearmost position to its armed or forwardmost position. In the armed position delay squib 114 and squib holder 10 are moved forward so that squib firing holes 112 are forward of seal 132 and within squib firing cavity 126; in this position, energization of delay squib 114 will cause activation of chemical delay 130 due to venting of the generated fluids through exit port 128.

Movement of the piston member provides a plurality of switching functions vbetween the ring contacts and the brushes. The two dotted lines next to each ring contact in FIG. 3 represent the armed (second) and firing (third) positions at the far right and intermediate, respectively, corresponding to the position of the piston member. The configuration of the electrical circuit when the fuze is in the armed or forwardmost position actuates the subsequent operations in the signal itself. First, explosive switch 180 is energized since seawater battery 74 becomes serially connected with the explosive switch by appropriate lead wires serially connecting one terminal of the switch to normally closed contacts 184, to brush 166, to contact ring 140, to the seawater battery, to contact ring 138, to brush 162, and lastly to the other terminal of the explosive switch. Second, gas generating squib 188 is energized since it is also serially connected to the seawater battery, via contact rings 138 and 140 and brushes 162 and 166, respectively, by appropriate lead wires. Third and fourth, detonator 180 and delay squib 114 are still maintained out of the circuit.

Upon energization of gas generating squib 188, a chemical reaction is initiated in the nose sectoin of signal 10, as can be best seen in FIG. 1. The chemical reaction thusly started generates a great volume of gas which, in turn, creates a high pressure build-up within an expansion chamber 198 in the nose of the signal. The resultant in crease in pressure within the expansion chamber drives piston 26, as well as inner casing 16 to which it is secured, down the cylinder defined by outer casing 14; this telescoping expansion between the inner and outer casings increases the volume of signal 10 thereby making it positively buoyant. During this expansion process, the volume of fluid trapped within annular chamber 20 is vented through ports 18. The telescoping expansion of the signal continues until the inner and outer casings are locked, by conventional means, in the fully extended configuration (not shown) wherein the length of signal 10 may be, by way of example, approximately 71.0 inches and wherein signal 10 may be sufliciently positive buoyant to cause the signal to rise to the surface at the rate of approximately 18 feet per second. As signal 10 begins to ascend, the hydrostatic pressure, which is urging piston member forward, will begin to decrease; and piston member 50, being urged rearward by spring 104, will begin to move rearward in response to the decrease in hydrostatic pressure.

Nearing surface and surface The piston member 50 continues to move rearward until, as the signal nears the surface, the piston member is locked into place at a firing or intermediate position between the safe and armed positions. The locking action may be most readily understood by reference to FIG. 4 wherein a portion of three insulating bushings 136, electrical contact rings 142 and 144, and electrical brush 174 are illustrated in the initial or safe position of the piston member. Initially, brush 174 bears against the left bushing 136 and is resiliently urged radially inward thereagainst by any conventional technique. When the signal is launched and the piston member moves to the second or armed position due to the maximum hydrostatic pressure, the bushings and contact rings move to the left, relative to stationary brush 174, as seen in FIG. 4. As the bushings and contact rings move to the left, forwardmost edge 196 of groove 192 passes brush 174 which then bears against flat bottomed surface 194 of the groove due to the aforementioned resilient, radially inward bias of the brush. The bushings and contact rings continue to move to the left until the piston member completes its forward stroke and is stopped by the engagement of flanges 94 and 106 as previously discussed. At this point brush 174 bears against flat bottomed surface 194 of groove 192 near the rearward extremity thereof, which would be near the right end as seen in FIG. 4. Finally, as the piston member begins to move rearward to the third or firing position due to the decrease in hydrostatic pressure as the signal ascends, the bushings and contact rings move to the right relative to fixed brush 174 until the brush engages forwardmost edge 196 of groove 192. Since brush 174 is urged radially inward, it cannot slide past edge 196 and thus serves to stop the rearward movement of the piston member. Although mechanical expedients may be employed to lock the piston member in the firing position, it should be noted that using the brush 174 as a stop member necessitates the end of the groove 192 occurring within contact ring 144. It is further contemplated that, by using electrical components having a fast time response, no locking means whatsoever would be required. In the firing position herein described, the squib firing holes 112 are still forward of seal 132 so as to provide open fluid communication between delay squib 114 and squib firing cavity 126 as in the armed position.

Referring now again to FIG. 3, it may be seen that detonator is energized by the serial connection of one terminal thereof to brush 162, to contact ring 138, to seawater battery 74, to contact ring 140, to brush 164, to normally open contacts 184 (now closed), and lastly to the other terminal of the detonator. Delay squib 114 is simultaneously energized by a similar circuit in that the delay squib, in the firing position is connected in parallel with detonator 190 via contact ring 144 and brush 174 and contact ring 146 and brush 176.

Reference to FIGS. 2 and 3 will illustrate the mechanical operations actuated by these electrical operations. As signal 10 nears the surface, it is necessary to separate inner casing 16 from the outer casing 14 in order to launch the pyrotechnic display package 11 contained within the inner casing. The outer casing must be removed to provide a closed end which may be easily opened through which the pyrotechnic display package may be ejected. Since the outer casing serves no operational purpose other than increasing the buoyancy of the signal, it is explosively separated by conventional means which are initiated by detonator 190. After the separation process is completed, the inner casing continues to rise to the surface but at a slower rate of ascent.

Simultaneously with the actuation of detonator 190 in the separation process, delay squib 114 is energized. The fluids generated thereby vent through squib firing holes 112, into squib firing cavity 126, through exit port 128, and activate chemical delay 130. The chemical delay ultimately initiates the display package ejection, but during this delay, which may suitably be approximately 11.0 seconds between the actuation of detonator 190 and the ejection, the outer casing 14 floats clear and away and the inner casing 16 stabilizes in the water at the surface in a vertical position with, by way of example, approximately 2.0 inches of freeboard. In this position the pyrotechnic display package 11 is ejected by conventional means which form no part of this invention. It should be understood that the fuze of the present invention has completed its requisite function upon initiating the chemical delay means. It should be further understood that the signal itself, particularly the pyrotechnic display package and ejection assembly, forms no part of the instant invention, but has been disclosed herein to the extent necessary to illustrate at least one environment in which the fuze might be used.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A hydrostatic fuze comprising a casing having a central axial cavity means defining an explosion chamber at one extremity of said cavity, having an inlet opening in communication with said cavity and having an exit port,

an elongate piston slidably positioned within said cavity in alignment with said explosion chamber inlet opening,

an explosive device secured to the end of said elongate piston nearest said explosion chamber,

a diaphragm connected between said casing and said piston so as to form a flight-tight seal therebetween,

a spring operatively interposed between said casing and said piston normally urging said piston away from said explosion chamber.

2. The fuze of claim 1 further comprising a plurality of electrical contacts axially spaced along the outer surface of said piston, and

a plurality of electrical contacts axially spaced along the inner surface of said axial cavity.

3. The fuze of claim 2 further comprising:

a seawater battery connected to two of said piston contacts and an explosive squib connected to two other of said piston contacts.

4. In a signal vehicle launchable from a underwater platform and having an expandable casing, means for expanding said casing, means including a detonator for explosively separating the signal vehicle into two segments, delay means, and an aerially displayable payload which may be launched subsequent to the activation of said delay means and in response thereto, a control device comprising:

piston means slidably mounted within said signal vehicle and adapted to be exposed to the ambient hydrostatic pressure so that a first force proportional to the hydrostatic pressure may be exerted on said piston means in a first direction,

resilient means urging against said piston means so that a second force may be exerted on said piston means in a second direction opposite to said first direction whereby the position of said piston means is proportional to the hydrostatic pressure;

first electrical means for initiating the casing expanding means in response to the launching of said signal vehicle whereby said signal vehicle will become positively buoyant; and

second electrical means for subsequently and simultaneously actuating said detonator and initiating said delay means in response to the nearing of the surface by said signal vehicle.

5. The apparatus of claim 4 further comprising first stop means for restraining said piston in a first position prior to launching said signal vehicle.

6. The apparatus of claim 5 further comprising second stop means for limiting at a second position the maximum movement of said piston means from said first position in response to the hydrostatic pressure at the launching of said signal vehicle.

7. The apparatus of claim 6 further comprising third stop means for limiting at a third position the maximum movement of said piston means from said second position in response to a decrease in hydrostatic pressure as said signal vehicle approaches the surface.

8. The apparatus of claim 7 wherein said second electrical means comprises an electrically energizable squib fixedly secured to said piston means and slidable therewith.

9. The apparatus of claim 8 further comprising means providing a cavity within said signal vehicle, said cavity having an inlet port and an exit port, said cavity furthermore being remotely positioned with respect to said squib when said piston means is in said first position but being closely positioned with respect to said squib when said piston means is in said third position.

10. The apparatus of claim 9 further comprising a squib holder fixedly secured to said piston means in such a manner as to encapsulate said squib within said squib holder and said piston means, said squib holder extending into said cavity through said inlet port, and said squib holder further being provided with a plurality of apertures positioned in said holder so as to be outside said cavity when said piston means is in said first position but inside said cavity when said piston means is in said second and third positions.

11. The apparatus of claim 10 further comprising sealing means positioned around said cavity inlet port so as to maintain a fluid-tight seal between said squib holder and said means providing a cavity.

12. An electrical circuit for use with a hydrostatically responsive electromechanical switching device having at least three discrete positions, comprising:

a plurality of impedance means; and

means for short circuiting each of a first, a second,

and a third of said impedance means and for open circuiting a fourth of said impedance means when the switching device is in a first discrete position, for connecting in parallel each of said first and third impedance means to a voltage source and for open circuiting each of said second and fourth impedance means when the switching device is in a second discrete position, and for connecting in parallel each of said second and fourth impedance means to said voltage source when the switching device is in a third discrete position.

13. The circuit of claim 12 wherein said first, second, third and fourth impedance means comprise first, second, third and fourth electrically energizable resistance means, respectively.

14. The circuit of claim 13 wherein said first, second, third and fourth electrically energizable resistance means comprise a first chemically reactive squib means, a detonating means, an explosive switching means, and a second chemically reactive squib means, respectively.

15. The circuit of claim 14 wherein the switching device efiects successive position changes in response to changes in hydrostatic pressure.

References Cited UNITED STATES PATENTS 2,827,850 3/1958 Muzzey l0216 2,974,588 4/1961 Fogal et a1. l0216 3,078,801 2/1963 Rzewinski et al. 10270.2 3,195,460 7/1965 Kalaf l0216 3,196,789 7/1965 Fasig et a1. l02-7 3,252,417 5/1966 Johnson l0216 VERLIN R. PENDEGRASS, Primary Examiner.

US. Cl. X.R. 102--70.2 

